1. Field of the Invention
This invention relates to an addition circuit for adding electrical signals representing two power or voltage values which are expressed in the decibel measurement system.
In the decibel measurement system, a power P is defined in terms of the function 10 log.sub.10 P. A signal voltage V representing this power gives a decibel measurement of 10 log.sub.10 V.sup.2, or 20 log.sub.10 V.
2. The Prior Art
The conventional system for adding two decibel measurements is, first, to convert each measurement back to a power or voltage measurement; then, to add these powers or voltages together, and finally, to convert the resultant total back again into the decibel form of measurement. For this conventional system to be effective, it is necessary to convert both voltage measurements into a linear form of mathematical expression.
In the patented prior art, there is a patent to Edwards, U.S. Pat. No. 4,011,509 which teaches a digital circuit for determining relative power measurements by storing a value representing a first power measurement and using that value as a reference for processing subsequent power measurements. Each value of power measurement is converted into a base 10 logarithm, and a ratio, in decibels, is obtained between each power measurement and the reference value.
Although the present invention utilizes some of the basic circuit component parts as in the Edwards digital circuit for his network analysis, the overall arrangement of the present invention, as well as the objectives of the invention, are totally different. These and other distinctions will become more apparent as the description proceeds.